This invention relates to electro-magnetic field transmission systems and more particularly, to reduction of crosstalk interference components due to mutual coupling in magnetic coils.
A problem may arise in electronics due to the mutual inductance when two or more electrical circuits having magnetic coils generating electromagnetic field are disposed relatively close one with respect to the other. Indeed, when oscillating electric currents in these coils are of high intensity, interference (hereafter referred to as crosstalk interference) may arise due to electromagnetic coupling between the magnetic coils. For instance, if a portion of the oscillating electromagnetic flux emanating from a magnetic coil of one electrical circuit intercepts a coil of an adjacent electrical circuit, then such stray flux from the first coil may cause undesirable crosstalk oscillating current in the second coil and vice versa. The frequency of this undesirable current in the second coil is equal to the frequency of the inducing electromagnetic flux in the first coil.
The problem of crosstalk interference may be even reinforced when resonance circuits, including a capacitor coupled with a coil, are used instead of a single coil. This may result in reducing the signal-to-noise ratio, and thereby will cause undesirable distortion of signals in the electrical circuits.
There is, accordingly, a need in the art to provide a technique for reducing components of the crosstalk interference in electrical circuits that include magnetic coils which are disposed relatively close one with respect to other.
In accordance with the invention, the reduction of the crosstalk interference is achieved by estimating the current crosstalk interference induced by certain neighboring coils into the given circuit; and, thereafter, by subtracting this crosstalk interference components from a multiplex electric current flowing through the magnetic coil of the given electrical circuit.
The invention, for instance, may be useful for electromagnetic multi-carrier transmissions wherein the electrical circuits are electromagnetic transmitters and crosstalk interference can be a substantial impediment to proper transmission of a signal. Such multi-carrier transmissions, for instance, may be utilized for the purpose of determining position and orientation of a moving object (see, for example, U.S. Pat. Nos. 4,314,251, 4,742,356, 4,849,692, 5,646,525 and the references thereof).
In accordance with a general aspect of the invention there is provided a system comprising at least two electric circuits, each electrical circuit having a magnetic coil with an oscillating multiplex electric current flowing therethrough; said oscillating multiplex electric current having a main current component, related to a given electrical circuit from among said at least two electric circuits, which is superposed with a current crosstalk interference component, originated from electromagnetic flux emanating from the magnetic coil of an at least one neighboring electrical circuit from among said at least two electric circuits and intercepted by the magnetic coil of the given electrical circuit, wherein each of said electrical circuits is configured to perform the following:
(a) estimating the crosstalk interference component induced by the at least one neighboring electrical circuit; and
(b) subtracting the crosstalk interference component from the current flowing through the magnetic coil of the given electrical circuit by using the crosstalk interference estimates obtained in (a);
whereby reduction of said current crosstalk interference component is achieved.
In accordance with a preferred embodiment of the invention, each of said electrical circuit comprising:
(i) an analog module incorporating a magnetic coil; and
(ii) a digital module coupled to said analog module via a digital-to-analogue converter and via an analog-to-digital converter, thereby forming a closed loop electric circuit; said digital module is configured to reduce said current crosstalk interference components.
In accordance with the invention, the digital module comprising an at least one Crosstalk Frequency Reduction Control Loop (CFRCL) for receiving said multiplex electric current from said analog-to-digital converter and providing a corrected signal to said analog module via the digital-to-analog converter for reducing the corresponding crosstalk interference component originated from the magnetic coil of the certain neighboring electrical circuit, said CFRCL comprising: a Phase Locked Loop unit coupled with said analog-to-digital converter; an All Pass Filter coupled with said digital-to-analog converter, and a Main Frequency Controller coupled with said Phase Locked Loop unit and said All Pass Filter.
In accordance with the invention, the digital module further comprising a Main Frequency Control Loop (MFCL) for receiving a multiplex electric current from the analog-to-digital converter, wherein the MFCL stabilizes a main current component of said multiplex electric current, related to the given electrical circuit, and provides a stabilized main current component to said analog module via the digital-to-analog converter, the MFCL comprising: a Phase Locked Loop unit coupled with said analog-to-digital converter, an All Pass Filter coupled with said digital-to-analog converter, and a Main Frequency Controller coupled with said Phase Locked Loop unit and said All Pass Filter.
In accordance with another general aspect of the present invention, there is provided a method for reducing a current crosstalk interference component from an oscillating multiplex electric current flowing through a magnetic coil of a given electrical circuit, oscillating multiplex electric current having a main current component, related to the given electrical circuit, which is superposed with said current crosstalk interference component originated from an electromagnetic flux emanating from a magnetic coil of a certain neighboring electrical circuit and intercepted by the magnetic coil of the given electrical circuit, the method comprising the steps of:
(a) estimating said current crosstalk interference component induced by the certain neighboring electrical circuit; and
(b) subtracting said current crosstalk interference component from a multiplex electric current flowing through the magnetic coil of the given electrical circuit by using crosstalk interference estimates obtained in step (a).